From 1b175025fecb1c10e6719d4ab79c188d473fccc4 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@duempel.org>
Date: Thu, 31 Jan 2013 20:33:26 +0100
Subject: pcm_*: convert to C++
---
src/PcmDither.cxx | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 93 insertions(+)
create mode 100644 src/PcmDither.cxx
(limited to 'src/PcmDither.cxx')
diff --git a/src/PcmDither.cxx b/src/PcmDither.cxx
new file mode 100644
index 000000000..e18119082
--- /dev/null
+++ b/src/PcmDither.cxx
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "PcmDither.hxx"
+#include "PcmPrng.hxx"
+
+static int16_t
+pcm_dither_sample_24_to_16(int32_t sample, struct pcm_dither *dither)
+{
+ int32_t output, rnd;
+
+ enum {
+ from_bits = 24,
+ to_bits = 16,
+ scale_bits = from_bits - to_bits,
+ round = 1 << (scale_bits - 1),
+ mask = (1 << scale_bits) - 1,
+ ONE = 1 << (from_bits - 1),
+ MIN = -ONE,
+ MAX = ONE - 1
+ };
+
+ sample += dither->error[0] - dither->error[1] + dither->error[2];
+
+ dither->error[2] = dither->error[1];
+ dither->error[1] = dither->error[0] / 2;
+
+ /* round */
+ output = sample + round;
+
+ rnd = pcm_prng(dither->random);
+ output += (rnd & mask) - (dither->random & mask);
+
+ dither->random = rnd;
+
+ /* clip */
+ if (output > MAX) {
+ output = MAX;
+
+ if (sample > MAX)
+ sample = MAX;
+ } else if (output < MIN) {
+ output = MIN;
+
+ if (sample < MIN)
+ sample = MIN;
+ }
+
+ output &= ~mask;
+
+ dither->error[0] = sample - output;
+
+ return (int16_t)(output >> scale_bits);
+}
+
+void
+pcm_dither_24_to_16(struct pcm_dither *dither,
+ int16_t *dest, const int32_t *src, const int32_t *src_end)
+{
+ while (src < src_end)
+ *dest++ = pcm_dither_sample_24_to_16(*src++, dither);
+}
+
+static int16_t
+pcm_dither_sample_32_to_16(int32_t sample, struct pcm_dither *dither)
+{
+ return pcm_dither_sample_24_to_16(sample >> 8, dither);
+}
+
+void
+pcm_dither_32_to_16(struct pcm_dither *dither,
+ int16_t *dest, const int32_t *src, const int32_t *src_end)
+{
+ while (src < src_end)
+ *dest++ = pcm_dither_sample_32_to_16(*src++, dither);
+}
--
cgit v1.2.3